The present invention relates in general to a conveyor system wherein vehicles on a track are propelled by a rotating drive shaft engaging with drive wheels on the bottom of the vehicles. A vehicle and track system of this type is disclosed in U.S. Pat. No. 3,818,837 issued June 25, 1974. The aforementioned patent discloses a vehicle having a speed control device on its rear end, in the form of cams and cam followers, which cooperates with a drive control member on the front end of an adjacent vehicle. Contact between a cam on one vehicle and the drive control member on the next vehicle causes the last mentioned vehicle to accumulate or stop by oscillating the drive wheel with respect to the drive shaft.
Another speed control device for these so-called driverless vehicles is disclosed in U.S. Pat. No. 3,903,810 issued Sept. 9, 1975. The speed control device disclosed in this patent also uses cams and cam followers to control the speed of the vehicle and to bring the vehicle to a complete stop, such as at a loading station.
The prior art vehicles and track systems discussed above have the disadvantage of requiring mechanical systems in the form of cams and cam followers to control the speed of the vehicle or to stop the vehicle. Another drawback of these systems is that the location of any vehicle on the track at any given time is not known without physically searching for the vehicle. A further drawback of these systems is that the speed and acceleration of each vehicle cannot be individually controlled.
It is therefore desirable to provide a driverless vehicle and track system which does not require the use of mechanical systems such as cams and cam followers to control the speed of the vehicles or to stop the vehicles to prevent collision therebetween. It is also desirable to provide a driverless vehicle and track system wherein the speed and acceleration of each vehicle can be individually controlled. It is further desirable to provide a driverless vehicle and track system wherein the exact location of each vehicle in the system is known at any given time.